Comparison of Actual and Allowable Stress Values for out-of-Plane Shear on Masonry Walls

This paper presents research results from the testing of 16 masonry wall specimens in direct out-of-plane shear. The wall specimens were two courses high and 1.2 m (48 in.) long. The walls were nongrouted and were constructed with face-shell bedding only. The testing apparatus was configured such that failure mechanisms other than direct out-of-plane shear (i.e., those resulting from flexural and axial loads) were minimized. Shear stress values from the 16 wall tests are compared with allowable shear stress values obtained in ACI 530 / ASCE 5 / TMS 402.

These results show that the code allowable shear stress values appear to be unconservative for this application of out-of-plane shear. It was found that the walls tested failed in out-of-plane shear at an average shear force of 69.8 kN (15,696 lb). This force produced an average shear stress of 0.349 MPa (50.65 psi) based on a parabolic stress distribution and 0.885 Mpa (128.36 psi) for pure shear stress.